Using unconstrained binary quadratic programming problem as a case study, we investigate the role of multi-parent crossover operators within the memetic algorithm framework. We evaluate the performance of four multi-parent crossover operators (called MSX, Diagonal, U-Scan and OB-Scan) and provide evidences and insights as to why one particular multi-parent crossover operator leads to better computational results than another one. For this purpose, we employ several indicators like population entropy and average solution distance in the population.